Toilet Seats and Loud Noises.
I am sure it is a male thing. We have three boys ranging in age from 9 to 19, and all have these habits (habits my wife has convinced me are annoying).
From the moment they learned how to pee, they leave the toilet seat up. (Why do women leave the toilet seat down?)
They stop listening very quickly, specially when you begin to repeat yourself.
They enjoy their bodily noises, and are quite fluent. It seems to be a question of practice and natural ability.
They love lavatory humor.
They fall asleep with a hand comfortably between their legs.
As they grow older they will probably graduate into the more annoying male habits, but as I told my wife, girls also have their fair share.